As the global population continues to climb and health trends encourage consumption of fish and crustaceans such as shrimp, ocean marine life populations worldwide are becoming depleted. According to the United States Food and Agriculture Organization (FAO), per capita fish consumption has increased from an average of 9.9 kg in the 1960s to 16.4 kg in 2005. The FAO has since reported that in 2009 about 88% of monitored fish stocks were overexploited, depleted, recovering from depletion, or fully exploited, which has resulted in devastating impacts to aquatic ecosystems worldwide. For example, in January of 2016, almost 300 species of fishes, clams, crustaceans were classified as either threatened or endangered. Further, harvesting wild marine life requires a large amount of fuel, about 620 liters per tonne of fish, which excludes the significant energy consumption for subsequent transport, cooling, and processing.
In recent years, aquaculture has been identified as a solution to the global marine sustainability crisis and a source of food for an ever expanding global population. This burgeoning industry includes the production and husbandry of aquatic plants and animals (e.g., fish, mollusks, and crustaceans) in controlled environments, such as tanks. Issues surrounding aquaculture have involved maintaining clean, efficient environments, maintaining a threshold level of dissolved oxygen within the water, and, in some circumstances, creating water current within the environment to satisfy the biological needs of inhabitant organisms.
Issues surrounding aquaculture have also involved scalability. While shallow-water raceways can be designed, developed, and implemented as laboratory-scale pilots, efforts to scale the pilots to, for example, commercially feasible dimensions have failed. The laboratory-scale pilots have used common airlift pumps and/or air-diffuser tubing to create and/or maintain required dissolved oxygen levels and/or create sufficient current to activate the raceway. However, when the same common airlift pumps and air-diffuser tubing have been used in scaled designs, the design has either completely failed, or the required dissolved oxygen levels and current cannot be maintained. The amount of horsepower required to drive high volume, low pressure air pumps for these types of scalable designs is not only inefficient, but also cost-prohibitive. Moreover, no stock size piping exists that is sufficiently large enough to convey the amount of air required for these designs. The common airlift pumps and common air-diffuser tubing were found to be inadequate for purposes relating to scalability.
FIG. 1 illustrates a commonly known air diffuser 100 utilized for oxygenating aquatic environments, which typically comprise an air source 110 in fluid communication with a diffuser stone, disk, tube, or disc 120. Air is directed through the diffuser 120 whereupon it is converted to a plurality of bubbles 130 which are more easily dissolved into the aquatic environment and cause less disruptive environmental turbulence than a single stream of air. Air diffusers suffer from the disadvantage that the diffuser is highly susceptible to fouling, and requires a large volume of air to sufficiently oxygenate an aquatic environment. Further, they produce little or no current.
Experimental aeration nozzles have been explored in academic settings as an alternative method for oxygenating aquatic environments, but in order to generate sufficient oxygenation, their use can generate a highly disruptive level of turbulence from discharge. Additionally, experimental aeration nozzles only provide current in a limited area and are not suitable for industrial scale vessels.